In recent years, high integration and high density in semiconductor device demands smaller and smaller wiring patterns or interconnections and also more and more interconnection layers. Multilayer interconnections in smaller circuits result in greater steps which reflect surface irregularities on lower interconnection layers. An increase in the number of interconnection layers makes film coating performance (step coverage) poor over stepped configurations of thin films. Therefore, better multilayer interconnections need to have the improved step coverage and proper surface planarization. Further, since the depth of focus of a photolithographic optical system is smaller with miniaturization of a photolithographic process, a surface of the semiconductor device needs to be planarized such that irregular steps on the surface of the semiconductor device will fall within the depth of focus.
Thus, in a manufacturing process of a semiconductor device, it increasingly becomes important to planarize a surface of the semiconductor device. One of the most important planarizing technologies is chemical mechanical polishing (CMP). In the chemical mechanical polishing, using a polishing apparatus, while a polishing liquid containing abrasive particles such as ceria (CeO2) therein is supplied onto a polishing pad, a substrate such as a semiconductor wafer is brought into sliding contact with the polishing pad, so that the substrate is polished.
The polishing apparatus for performing the above CMP process includes a polishing table having a polishing pad, and a substrate holding device, which is referred to as a top ring, a polishing head or the like, for holding a semiconductor wafer (substrate). By using such a polishing apparatus, the substrate is held and pressed against the polishing pad under a predetermined pressure by the substrate holding device to polish an insulating film, a metal film or the like on the substrate.
After one or more substrates have been polished, abrasive particles and polishing debris are attached to a surface of the polishing pad, the properties of the polishing pad are changed, and thus the polishing performance is deteriorated. Therefore, as the substrates are repeatedly polished, a polishing rate is lowered and non-uniform polishing is caused. Thus, dressing of the polishing pad is performed to regenerate the surface condition of the polishing pad which has deteriorated.
A dressing device for dressing the polishing pad includes an oscillatable arm and a dresser fixed to a distal end of the arm. In the dressing device, while the dresser is oscillated in a radial direction of the polishing pad by the arm and is rotated about the axis of the dresser, the dresser is pressed against the polishing pad on the rotating polishing table. Thus, the polishing liquid and the polishing debris which have been attached to the polishing pad are removed, and the polishing pad is planarized and dressed. The dresser having a surface (dressing surface), which is brought into contact with the pad surface, on which diamond abrasive particles are electrodeposited is used.
Conventionally, while a dressing liquid comprising pure water (DIW) having a predetermined temperature (e.g., approximately 20° C.) is supplied at a constant flow rate onto the polishing pad, dressing is performed for a predetermined time under the condition that the rotational speed, the dressing load, and the oscillating speed of the dresser are kept constant, respectively. During dressing, neither temperature control of the polishing pad nor monitoring of the surface roughness of the polishing pad is performed.
The surface of the polishing pad is roughened by dressing, and the surface roughness of the polishing pad has a correlation with a polishing rate. On the other hand, the surface roughness of the polishing pad is thought to be influenced by temperature of the polishing pad in addition to the conventional dressing conditions.